i too am interested in a bb downgrade in the case i get in any problems, i too have bootloader 5.08.
Im still running beta 3 jailbroken fine..no expiring. cause since my udid ain't registered can't go to beta 4 or 5

Does not work on Win7 not to surprised, just thought I would make it known

Yeah - just tried it on Win7 RC1 (7100) and it comes up with the error saying that the IPSW file doesn't match the firmware of my device. Strange because it is the exact same IPSW file I used to update to beta5. I also tried it in compatability mode for both Vista and XP and running as administrator.

Does not work on Win7 not to surprised, just thought I would make it known

I'm on windows 7... So please do not tell me that it does not work on it.

kthxbye

EDIT:

OK after reading another post the only way it'll give you that error is if you did not place the .bundle folder in the bundles directory of quickpwn or did not use a compatible quickpwn to attempt the jailbreak